The number of individual glycoproteins reported to be present in extracellular human cytomegalovirus (HCMV) has varied. Furthermore, little detailed information has been reported on the interactions and composition of HCMV glycoproteins. HCMV glycoproteins appear to be involved in human immune recognition of the virus. This has been demonstrated by the reactivity of HCMV glycoproteins with human convalascent sera. (G. H. Farrar et al., J. Gen. Virol., 65, 1991 (1984); B. Nowak et al., Virology, 132, 325 (1984)). Biochemical approaches have been used to try to determine the number and composition HCMV glycoproteins. Farrar et al., cited above, were able to detect five polypeptides in the membranes of HCMV strain AD169 which were labeled by carbohydrate-specific methods. These glycoproteins had molecular weights ranging from 57,000 to 250,000. One method they employed labeled galactose (Gal) and/or N-acetylgalactosamine (GalNAc) residues. With this method, two glycoproteins with molecular weights of 67,000 and 130,000 showed relatively high incorporation of label suggesting that these glycoproteins have a distinct phenotype marked by relatively high concentrations of Gal and/or GalNAc and possibly high amounts of O-linked oligosaccharides.
Immunological approaches have also been used to try and identify the number of glycoproteins in HCMV. Several laboratories have generated monoclonal antibodies which recognize one or more disulfide-linked glycoprotein complexes which contain three individual glycoproteins. Several laboratories have reported molecular weights of 130,000, 92-95,000, and 52-55,000 for these glycoproteins (G. Farrar et al., J. Gen. Virol., 67, 1469 (1986); B. E. Kari et al., J. Virol., 60, 345 (1986); K. M. Law et al., J. Med. Virol., 17, 255 (1985); L. Rasmussen et al., J. Virol., 55, 275 (1985)). Kari et al. have disclosed two monoclonal antibodies (41C2 and 9B7) which recognize these glycoproteins. Hereinafter, the parent glycoprotein complex will be referred to as gCI. However, a continuing need exists to identify and characterize HCMV glycoprotein complexes and their constituent glycoproteins ("glycopeptides"), particularly those which can elicit a protective immune response.